Process for casting metals.



F. DE BUIGNE. PROCESS FOR. CASTING METALS. APPLIOATION FILED OCT. 14, 1911.

1 1,026,733. Pat ntedMay21, 1912.

Witnesses: fifiventor. M ma aat torney UNITED STATES PATENT ornr FRANZ, De 3mm, OF MAGDEBURG, GERMANY.

rnoonss non CASTING METALS.

To ZiZZ whom it may concern:

Be it known that I, FRANZ DE BUIGNfi, a subject of the Austro-Hungarian Emperor, and resident of Magdebu-rg, in the Kingdom of Prussia, German Empire, have invented a new and useful Improved Process for Cast ing Metalsfof which the following is a full,

clear, and exact specification.

. This invention relates to a process for casting metals under pressure, that is, particularly diflicult fusible metals such as iron, bronze, aluminium or the like.

The invention consists in melting the metal by internal heating in a container, or main taining the metal molten by internal heating in the container, during the casting operation. I

Hitherto the casting metals under pressure has generally been effected through external heating. In the event of metals to be cast being of high melting point and when high pressures are used external heating has its disadvantage, is difficult or impossible to keep the walls of the furnace or crucible sufliciently resistant at these high temperatures. According to this invention the heating is from within and in consequence it is possible to keep the outside of the crucible or furnace by choice of suitable constructional material and suitable thickness ofiwall and if necessary by cooling devices, suificiently cool to insure the desired degree of resistance to mechanical pressure or gas pressure, such as is unavoidable in the process of casting under pressure, without disturbing the melting operation.

The contents of the crucible may be heated in various ways; for example by introducing a flame of gas under pressure. In" many cases 1t is advantageous to use electrlcal heating. o

In the accompanying drawing the invention is illustrated diagrammatically, a vertical section through an electric furnace being shown by way of example. 7

, a is the hearth of the melting and heating chamber, a is the cover, 6 the external castrodes, e the delivery ing, 0 the molten bath, d and d the elecpipe for the molten metal, f the part of thls pipe which is external to the furnace chamber.

g is the pipe for the supply of the gaseous pressure medium, 72, is a branch of this pipe and communicates with 'the atmosphere; z is a spring pressed admission valve in the pipe 9, k is a spring pressed exhaust valve in the Specification of Letters Patent.

Application filed October 14, 1911.

Serial No. 654,781.

cases carbon, which may be mixed with refractory clay or the like, is used. The cover a is of any suitable material. The electrodes d and d are preferably movable, being made tight by means of stufling boxes or the like. It is also possible to use the hearth in known manner as one pole, in which case a suitable device for supplying current is provided.

For starting the casting operation, the spring pressed admission valve 91 is opened. The gaseous pressure medium enters the furnace through pipe 9 and forces a certain quantityof the molten metal through the pipe 6. Against the upper end f of the delivery pipe e, a suitable mold is pressed. When the spring pressed valve'z' has been closed, the spring pressed valve is is opened, whereby pressure is relieved and the casting operation interrupted. The pipe 6 is preferably contracted as shown in the drawing for a length about equal to the height of the furnace and is then expanded up to the delivery end, as shown at f. The object is thus achieved that when toward the end of the casting operation a part of the metal-in the pipe'solidifies, this part can be withdrawn as a lug attached to the object cast. The nonsolidified portion of the metal in the deliv ery pipe returns to the metal .bath as soon as the pressure has been relieved. This construction of the delivery pipe does not form I a part of this invention.

By opening the spring controlled exhaust valveJc the compressed gaseous medium 1s allowed to escape very rapidly from the melting chamber, so that a diminished pressure is produced which exerts a suction on the delivery pipe and draws back the excess of metal into the bath. This action is of particular importance when the delivery pipe is more horizontally placed than as shown in the drawing. Moreover, the sud- Patented May 21, 1912.

den release of the gas pressure by opening terior is solid, the liquid metal may be sucked back from the interior of the casting by the aforesaid suction, into'the melting chamber. This suction can be aided, if desired, by connecting'pipe h with avacuum pipe at the same time that valve is is opened.

In many cases it is advantageous that a gas which is indifferent to the molten metal should be used as pressure medium. For instance, nitrogen, carbon dioxid or another gas suitable for the individual case, may be used. This presents the advantage that the electrodes and furnace lining, so far as the latter consists for instance of carbon, are much economized, and the metal bath remainsvery pure, because oxidation of the bath by the gaseous pressure medium is avoided and the introduction of considerable quantities of electrode ashes are avoided, both of which sources of impurity were hitherto inevitable.

The delivery pipe is shown in the draw ing in one position, but according to the v kind of object to be cast and the mold to be used, it may have any other upwardly, laterally or downwardly directed position.

By the present process and apparatus 1 large or small objects which may be solid or hollow, may be cast; the whole contents of the metal bath may be used at once for making a correspondingly large article, or only a comparatively small quantity of metal may be used for each casting operatlon, so that the contents of the furnace suflices for a large number of separate castings; the metal consumed can be made good either continuously or periodically.

What I claim is:

1. In a process of casting molten metals under pressure, which consists in heating a metal bath internally, suddenly releasing the pressure established by an indifferent gas so as to produce by the rapid escape of the gases a partial vacuum in the melting chamber, substantially as and for the purposes described.

2. In a process of casting molten metals under pressure, which consists in heating a metal bath internally by means of electric- 1ty, suddenly releasing the pressure established by an indifferent gas so as to prometal ath internally, suddenly releas ng the pressure established by an indifferent gas so as to produce by the rapid escape of the gases a partial vacuum in the melting chamber and then increasing the vacuum thus created, substantially as and for the purposes described.

4. In a process of, casting molten metals under pressure, which conslsts in heating a metal bath internally by means of electricity, suddenly releasmg the pressure established by an indifferent gas so as to produce by the rapid escape of the gases a partial vacuum in the melting chamber and then increasing the vacuum thus created, substantially as and for the purposes described.

5. In a process of castin molten metals under pressure, which conslsts in heating a metal bath internally by means of electricity, maintainin an atmosphere of an indifferent gas a ove the molten metal, re-

leasing the pressure to establish a partial 6. In a process of casting molten metalsunder pressure, which consists in heating a metal bath internally by means of electricity, supplying an indiiferent gas as a pres sure medium, releasing the pressure to produce a partial vacuum and finally increasing the same, substantially as and for the purposes described. 1

7. In a process of casting'molten metals under pressure, which consists in heating a metal bath internally by means of electricity, suddenly releasing the pressure to produce a partial vacuum in the melting chamber and then increasing the same, substantially as and for the purposes described.

8. In a process of casting molten metals under pressure, which consists in heating a metal bath internally by means of electricity, suddenly releasing the pressure to produce a' partial vacuum in the melting chamber and increasing the vacuum by connecting the chamber with a vacuum pipe, substantially as and for the purposes described.

9. In a process of casting molten metals under pressure, which consists of internally heating a metal bath held in a gas-tight conditlon under pressure, releasing the pressure and establishing a vacuum in the chamber in which the metal bath is held'and then increasing the vacuum thus created, substantially as and for the urposes described.

In testimony, that I c aim the foregoing as my invention, I have signed my name in 

